I upgraded my old deck to composite decking. The composite deck boards worked with hidden fasteners, but the composite boards on the stairs required me to drill down into them. I couldn't find any plugs to cover the screw heads from the major retail hardware store, the manufacturer, or online. The manufacturer recommends taking some shavings from drilling, wadding them up, tucking them over the screw, and hammering it. The board on the left shows the screw heads and the board on the right shows the shavings hammered over them. I didn't like the results.
Step 1: Hollow Punch Set
I thought I was stuck hammering shavings until I stumbled across a hollow punch set at a tool store. I found the 3/16" hollow punch to fit perfectly over the composite decking screws. Use a hammer drill on a scrap piece of decking to punch out holes.
Step 2: Making the plugs
Once the hollow punch goes all the way through, pull it out. Then use a nail or something similar to push the plug out of the punch. Then slice the pieces to about 1/8" pieces with a razor blade knife.
Step 3: Finishing up
Put the plugs over the screw heads and hit them with a hammer. If the plugs are too big, then it will mushroom out. Use a razor blade to cut some of the excess off the outside and hit it with a hammer again. Voila! Screw heads covered up with matching plugs.